Bsi bs en 60904 4 2009

raising standards worldwide™ NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI Standards Publication Photovoltaic devices — Part 4 Reference solar devices — Procedures for est[.]

NO COP YING WITHOUT SI P ERMIS ION EX EP T AS P ER MITTED BY COP YR IGHT L AW

Pho to vo ltaic devic es —

Part 4 : Reference s olar devices — Procedures

for es tabl s hing cal bration traceabi ity

Nat io al fore word

T is Brit ish St an ard is t he U imple me nt at ion of EN 60 04 -4 :2 0 It is

ide nt ic l t o IEC 60 04-4:2 0

T e UK part ic ipat ion in it s pre parat ion was e nt rust e d t o Te c hnic l C ommit t e e

GE /8 , Solar phot ovolt aic e ne rg syst e ms

A ls of organiz t ions re pre se nt e d on t his commit t e e c n be o t aine d on

re que st t o it s se cre t ary

T is publc at ion doe s not purp r t o inclu e al t he ne c e ssary provisions of a

c ont ra t Use rs are re sp nsible for it s core ct ap lc at ion

© BSI 2 10

ISBN 9 8 0 5 0 64 261 6

ICS 2 160

C omplance wit h a Brit ish St andard can ot co fe r immu it y f om

le gal obl gat ions

This B t ish St an ard was p blshe d u de r t he aut ho t y of t he St an ards

P lc y an St rat e gy C ommit t e e o 31 Jan ary 2010

Ame ndme nt s is ue d since pu lcat ion

Amd No Dat e Te xt afe ct e d

NOR ME EUR OPÉENNE

EUROPÄISCHE NORM

Nov ember 2009

Euro e n Committee for Electrotechnical Stan ardiz ation

Comité Euro é n de Normalsation Electrotechniq e

Euro äisches Komitee für Elektrotechnische Normu g

Ce ntra l Se cre ta ria t: Ave nu Ma rnix 17, B - 10 0 Bru se ls

© 2 0 CENELEC - All rig t s of ex ploit at io in a y form a d b a y me n re erv d worldwid for CENELEC memb rs

ICS 2 16

En ls v ersion

Photovoltaic dev ices -

Part 4: R eference solar devices -

Procedures for establ shing cal bration traceabi ity

(IEC 60904-4:2009)

Disposit ifs phot ov olt ạques -

Part ie 4: Disposit ifs solaires d référe c e

-Proc édures p ur ét ablr

la t raç abi t é de lét alonnage

(CEI 60904-4:2009)

Phot ov olt aisc he Einric ht ungen -

Tei 4: R eferenz-Solarelement e -

V erahren z r Fest st elung

der Rüc k v erolgbark eit der K albrierung

(IEC 6 904-4:2009)

This Euro e n Sta d rd was a proved b CENELEC o 2 0 -0 -01 CENELEC memb rs are b u d to c mply

with the CEN/CENELEC Intern l R eg lat io s which stip late th c n itio s for givin this Euro e n Sta d rd

the status of a n tio al sta d rd with ut a y alteratio

Up-to-d te lsts a d biblo ra hical refere ces concernin such n tio al st an ards ma b o tain d o

a plcatio to the Ce tral Se retariat or to a y CENELEC memb r

This Euro e n Stan ard e ists in thre oficial versio s (En lsh, Fre ch, Germa ) A versio in a y other

la g a e ma e b tra slatio u d r th resp nsibi ty of a CENELEC memb r into its own la g a e a d n tifie

to the Ce tral Se retariat h s the same status as the oficial versio s

CENELEC memb rs are the n tio al ele trotec nic l c mmitt es of Austria, Belgium, Bulg ria, Cy rus, the

Cz ec Rep blc, De mark, Estonia, Finla d, Fra ce, Germa y, Gre c , Hu g ry, Icela d, Irela d, Italy, L tvia,

Lith a ia, L xemb urg, Malta, the Netherla ds, Norwa , Pola d, Portu al, R oma ia, Slovakia, Slovenia, Sp in,

Swe e , Switz erla d a d th Unite Kin d m

R ef No EN 6 9 4-4:2 0 E

The t ex t of doc ument 8 /53 /CDV , fut ure edit ion 1 of IEC 6 9 4-4, pre ared b IEC TC 8 , Solar

phot ov olt aic energy sy st ems, w as s bmit t ed t o t he IEC-CENELEC p ralel v ot e an w as a prov ed b

CENELEC as EN 6 9 4-4 on 2 0 -0 -01

The folow in dat es w ere fix ed:

– lat est dat e b w hic h t he EN has t o b implement ed

at nat ional lev el b publc at ion of an ident ic al

nat ional st an ard or b en orsement (do ) 2 10-0 -01

– lat est dat e b w hic h t he nat ional st an ard c onflc t in

w it h t he EN hav e t o b w it hdraw n (dow ) 2 12-0 -01

Anne ZA has b en ad ed b CENELEC

_ _ _ _ _

Endorsement notice

The t ex t of t he Int ernat ional St an ard IEC 6 9 4-4:2 0 w as a proved b CENELEC as a Euro e n

St an ard w it hout any modific at ion

In t he ofic ial v ersion, for Biblogra hy , t he folow in not es hav e t o b ad ed for t he st an ard in ic at ed:

IEC 6 8 1 NOT Harmo iz d a EN 6 8 1:19 4 (n t mo ifie )

IEC 6 9 4- NOT Harmo iz d a EN 6 9 4- :2 0 (n t mo ifie )

IEC 6 9 4-3 NOT Harmo iz d a EN 6 9 4-3:2 0 (n t mo ifie )

IEC 6 9 4-7 NOT Harmo iz d a EN 6 9 4-7:2 0 (n t mo ifie )

IEC 6 9 4-8 NOT Harmo iz d a EN 6 9 4-8:19 8 (n t mo ifie )

IEC 6 9 4-9 NOT Harmo iz d a EN 6 9 4-9:2 0 (n t mo ifie )

IEC 618 6 NOT Harmo iz d a CLC/TS 618 6:2 0 (n t mo ifie )

_ _ _ _ _

A nnex ZA

(normat iv e)

Normat iv e references t o int ernat ional publ cat ions

wit h t heir cor esponding European publ cat ions

The folow in referenc ed doc ment s are in isp n a le for t he a plc at ion of t his doc umen F r dat ed

referenc es, only t he edit ion c it ed a ples F r u dat ed referenc es, t he lat est edit ion of t he referenc ed

doc ument inc lu in any amen ment s) a ples

NOT W he a int ern t io al p blc at io h s b e mo ifie b c ommo mo ific at io s, in ic at ed b (mo ), t he relev ant EN/HD

a ple

IEC 6 9 4-2

-1)

Phot ov olt aic dev ic es -

Part 2: R eq irement s for referenc e solar

General req irement s for t he c omp t enc e of

t es n an c albrat ion la orat ories

EN ISO/ IEC 17 2 2 0

2)

ISO/ IEC Guide 9 -3 2 0 Unc ert aint y of me s rement -

Part 3: Guide t o t he ex pres ion of u c ert aint y

in me s rement GUM:19 5)

-1)

Solar energy - Calbrat ion of field

py rhelomet ers b c omp rison t o a referenc e

Fig re 1 – Sc ematic of most common ref eren e in truments an tran fer method

u ed in the trace bi ty c ain for solar ir adian e detectors 7

Fig re A.1 – Bloc diagram of dif ferential sp ctral resp n ivity cal bration

s p rimp sin c o p d monoc romatic radiation DE(l an DC bias radiation E

b 18

Fig re A.2 – Optical ar an ement of diff erential sp ctral resp n ivity cal bration .19

Fig re A.3 – Sc ematic a paratu of the solar simulator method .21

Ta le 1 – Examples of ef eren e in truments, u ed in a trace bi ty c ain of time an

solar ir adian e .7

Ta le A.1 – Typical u certainty comp nents (k = 2) of glo al s nl g t method 15

Ta le A.2 – Typical u certainty comp nents (k = 2) of a dif ferential sp ctral

resp n ivity cal bration 18

Ta le A.3 – Example of u certainty comp nents (k = 2) of a solar simulator method

cal bration 21

Ta le A.4 – Typical u certainty comp nents (k = 2) of a solar simulator method

cal bration when WRR trace ble cavity radiometer is u ed 21

Ta le A.5 – Typical u certainty comp nents (k = 2) of a direct s nl g t method 2

PHOTOVOLTA IC DEVICES –

Part 4: Reference solar devices –

Procedures f or establ shing cal bration traceabi ity

1 Scope and object

This p rt of IEC 6 9 4 sets the req irements f or cal bration proced res inten ed to esta l s

the trace bi ty of photovoltaic ref eren e solar devices to SI u its as req ired by IEC 6 9 4-2

This stan ard a pl es to photovoltaic (PV) ref eren e solar devices that are u ed to me s re

the ir adian e of natural or simulated s nl g t f or the purp se of q antifyin the p rf orman e

of PV devices The u e of a PV referen e solar device is req ired in the a pl cation of

IEC 6 9 4-1 an IEC 6 9 4-3

This stan ard has b en writ en with sin le ju ction PV ref eren e solar devices in min , in

p rtic lar cry tal ne Si con However, the main p rt of the stan ard is s ff i iently general to

in lu e other tec nologies The method des rib d in An ex A, however, are lmited to sin le

ju ction tec nologies

2 Normative references

The f ol owin ref eren ed doc ments are in isp n a le f or the a plcation of this doc ment

For dated ref eren es, only the edition cited a pl es F r u dated ref eren es, the latest edition

of the referen ed doc ment (in lu in any amen ments) a pl es

IEC 6 9 4-2, Ph t ovolt aic d evic s – Part 2: Re uireme ts for refere c sol ar d evic s

ISO/IEC 17 2 , Ge eral re uireme ts for t he c mp t en e of t esting a d c l i ration

lab rat ories

ISO 9 5 , Solar e erg – Calibration of field p rh l iometers b c mp riso to a refere c

p rh liometer

ISO 9 4 , Sol ar e erg – Calibrat ion of a p ra omet er using a p rh l i meter

ISO/IEC Guide 9 -3: 2 0 , Un ert ainty of me sureme t – P art 3: Guid e t o t he ex pres io of

u c rtainty in me sureme t (GUM: 19 5)

3 Terms and def initions

For the purp ses of this doc ment, the f ol owin terms an definition a ply

NOT Th dif fere t refere c in trume ts for th tra e bi ty c ain of s lar ira ia c are d f i e in this Cla s

Ta le 1 lsts a d c mp re th m with th s in u e for time Fig re 1 s ows s h matic ly th mo t c mmo

tra e bi ty c ain , b s d o th meth d d s rib d in An e A

3.1

primary sta dard

a device, whic implements phy ical y one of the SI u its or directly related q antities They

are u ual y maintained by national metrolog in titutes (NMIs) or simi ar organisation

entru ted with maintenan e of stan ard for phy ical q antities Of ten ref er ed to also ju t as

an re e ta i ty of me s rement of the q antity it re resents are g arante d to the maximum

extent p s ible by c r ent tec nology

NOT Th World Ra iometric Refere c (WR ) a re lz d b th World Sta d rd Gro p (WSG) of c vity

ra iometers is th a c pte primary sta d rd for th me s reme t of s lar ira ia c

3.2

s condary sta dard

a device, whic by p riodical comp rison with a primary stan ard, serves to maintain

conformity to SI u its at other places than that of the primary stan ard It do s not neces ari y

u e the same tec nical prin iples as the primary stan ard, but strives to ac ieve simi ar lon

-term sta i ty, precision an re e ta i ty

NOT Ty ic l s c n ary sta d rd for s lar ira ia c are c vity ra iometers whic p rticip te p rio ic ly

(n rmaly e ery 5 y ars) in th Intern tio al Pyrh lometer Comp ris n (IP ) with th WSG

3.3

primary refere c

the ref eren e in trument whic a la oratory u es to cal brate secon ary referen es It is

comp red at p riodic intervals to a secon ary stan ard Often primary referen es can b

re l sed at mu h lower costs than secon ary stan ard

NOT Ty ic ly a s lar c l is u e a a refere c s lar d vic for th me s reme t of n tural or simulate s lar

ira ia c

3.4

s condary refere c

the me s rement device in u e for dai y routine me s rements or to cal brate workin

referen es, cal brated at p riodic intervals to a primary ref eren e

NOT Th mo t c mmo s c n ary refere c s for th me s reme t of n tural or simulate s lar ira ia c are

s lar c ls a d s lar mo ule

3.5

tra e bi ity

the req irement for any PV ref eren e solar device, to tie its cal bration value to SI u its in an

u broken an doc mented c ain of cal bration tran fers in lu in stated u certainties

NOT Th WR h s b e c mp re twic to th SI ra iometric s ale a d s own to b within th ir mutu l

u c rtainty le els Th refore tra e bi ty to WR a tomatic ly pro id s tra e bi ty to SI u its Howe er, th

u c rtainty of th ratio WR /SI u its n e s to b ta e into a c u t Th World Ra iatio Ce ter (WRC)

re omme d a re ta g lar u c rtainty distrib tio with 0,3 % h lfwidth A third c mp ris n is c re tly u d rwa

a d s o ld b p bls e in th f uture

J Romero, N.P Fo , C Frö lc metrolo ia 2 ( 9 1 12 -8

Table 1 – Ex mple of ref ere c instrume ts, us d in a tra e bi ity c ain

of time a d solar ir a ia c

Referenc instrument Time S lar iradianc

Primary sta d rd Ce ium atomic clo k at

Natio al Metrolo y In titute

(NMI)

Gro p of c vity ra iometers c n titutin th World Sta d rd

Gro p (WSG) of th World Ra iometric Refere c (WR )

Cry g nic tra d te tor

Sta d rd lamp

Se o d ry sta d rd Ce ium atomic clo k o GPS

(Glo al Po itio in Sy tem)

s tel te

Commercialy a aia lec vity ra iometers c mp re e ery 5

y ars at th Intern tio al Pyrh lometer Comp ris n (IP )

Sta d rd d te tor c lbrate a ain t atra d te tor

Sp ctrora iometer c lbrate a ain t a sta d rd lamp

Primary refere c GPS re eiv r, s t to s ow

time

Normal in id n e p rh lometer (NIP) (ISO 9 5 )

Refere c s lar d vic (IEC 6 9 4-2 a d IEC 6 9 4-4)

Se o d ry refere c Qu rtz watc Pyra ometer (ISO 9 4 )

Refere c s lar d vic (IEC 6 9 4-2)

NOT Dire t tra e bi ty of a s lute ra iometers to SI ra iometric s alema als b a aia le

Figure 1 – Sc ematic of most common ref ere c in trume ts a d tra sf er method

us d in the tra e bi ity c ains for solar ir a ia c d te tors

4 Requirements f or trace ble cal bration procedures of PV ref erence solar

devic s

A trace ble cal bration proced re is neces ary to tran fer cal bration fom a stan ard or

ref eren e me s rin solar ir adian e (s c as cavity radiometer, pyrhel ometer an

pyranometer) to a PV referen e solar device The req irements f or s c proced res are as

a) An me s rement in trument req ired an u ed in the tran f er proced re s al b an

in trument with an u broken trace bi ty c ain

b) A doc mented u certainty analy is

c) Doc mented re e ta i ty, s c as me s rement res lts of la oratory intercomp rison, or

doc ments of la oratory q alty control

d) Inherent a solute precision, given by a lmited n mb r of intermediate tran f ers

NOT 1 Normaly th tra sfer wo ld b fom a s c n ary sta d rd to a P ref ere c s lar c l c n titutin a

primary refere c

NOT 2 Th tra sf er f rom o e ref ere c s lar d vic to a oth r is c v re b IEC 6 9 4-2

5 Uncertainty analysis

An u certainty estimate ac ordin to MISC UNCERT – ED 1.0 (19 5-01) s al b provided f or

e c trace ble cal bration proced re This estimate s al provide inf ormation on the

u certainty of the cal bration proced re an q antitative data on the fol owin u certainty

f actors for e c in trument u ed in p rf ormin the cal bration proced re In p rtic lar:

a) Comp nent of u certainty arisin fom ran om eff ects (Typ A)

b) Comp nent of u certainty arisin f om s stematic eff ects (Typ B)

Nevertheles a ful u certainty analy is has to b p r ormed for the implementation of the

cal bration method by a p rtic lar la oratory

6 Cal bration re ort

The cal bration re ort s al conform to the req irements of ISO/IEC 17 2 an s al normal y

in lu e at le st the f ol owin information:

a) title (e.g ”Calbration Certificate” ;

b) name an ad res of la oratory, an location where the tests an /or calbration were

car ied out, if dif ferent f rom the ad res of the la oratory;

c) u iq e identif i ation of the re ort (s c as serial n mb r) an of e c p ge, the total

n mb r of p ges an the date of is ue;

d) name an addres of the cl ent placin the order;

e) des ription an u ambig ou identification of the item(s) tested or cal brated;

f ) date of receipt of cal bration item(s) an date(s) of p r orman e of test or cal bration, as

The cal brated referen e solar device s al b marked with a serial numb r or referen e

n mb r an the f olowin inf ormation atac ed or provided on an ac omp n in certificate:

b) calbration value an its temp rature co ff i ient (if a pl ca le).

Annex A

(inf or mativ )

Examples of val dated cal bration procedures

A 1 General

This an ex des rib s examples of calbration proced res for PV ref eren e solar cels as

primary referen e devices, together with their stated u certainties These proced res serve to

esta l s the trace bi ty of referen e solar devices to SI u its as req ired by IEC 6 9 4-2

Primary ref eren e devices cal brated in ac ordan e with these proced res serve to esta l s

the trace bi ty of f urther PV ref eren e solar devices

As alre d mentioned in Clau e 1, the method in this an ex are l mited to PV sin le ju ction

tec nolog More ver, they have c r ently only b en val dated f or cry tal ne Si con

tec nolog , althou h they s ould b a pl ca le to other tec nologies

The method have b en implemented in variou la oratories arou d the world an valdated

in international intercomp rison , most nota ly the World Photovoltaic Scale (WPVS)

However, the des ription in this stan ard is more general sed For detai s of the variou

implementation , the referen es in p er reviewed publcation are given at the en of e c

proced re

The u certainty estimates are b sed on U

9(coverage f actor k = 2) for al sin le comp nents

The combined exp n ed u certainty is calc lated as the s uare ro t of the s m of s uares of

al comp nents The un ertainties provided are simpl f ied version (restricted to the main

comp nents) as provided by the la oratories havin implemented the proced re These

u certainty calc lation serve as g idel nes an wi have to b ada ted to the p rtic lar

implementation of e c proced re in a given la oratory The u certainties ac ieved by an

implementation of these method mig t b con idera ly dif ferent Un ertainties q oted have

to b b sed on an expl cit analy is an can ot b taken by referen e to the u certainty

estimates in this stan ard

temp rature co ff i ient α of the s ort-circ it c r ent (IEC 6 8 1) normal zed to

the s ort-circ it c r ent at 2 °C an expres ed in 1/ °C

MMF mismatc f actor (se b low)

S (λ) sp ctral resp n e of referen e cel

s(λ) diff erential sp ctral resp n ivity of referen e cel

The method des rib d in Clau es A.2, A.4 an A.5 have some common calc lation , whic

are detaied in this s bclau e Detais of the variou implementation are then des rib d in

SCGSC2

SC

mW

10 0

)

W m

0 0(1

GI

MI

−

(A.1)

STC man ate a device temp rature of 2 °C, but me s rements wi not alway b taken at

this temp rature The deviation in temp rature s ould b ac ou ted f or in the u certainty

bu get It is also p s ible to cor ect I

TjSCSC

C21

)(

)(C)(2

TT

TI

MTII

The cor ection for the diff eren e in sp ctral sen itivity of the referen e cel to b cal brated

an the device u ed to me s re the ir adian e can b des rib d as a MMF

nm

4 0

nm

3 0m

)(

)()(

)()(

λλ

λλ

λλλ

λλλ

dE

dE

dES

dES

NOT Th inte ratio ra g is ta e b s d o th d f i itio of E

sλ) If th me s reme t ra g , in p rtic lar th t

of E

m

(λ), d e n t c v r this e tire ra g , s ita le a pro imatio , e tra olatio or mo el n c n b u e , b t

n e s to b a c u te f or in th u c rtainty c lc latio

The cal bration value CV of the referen e cel is then calc lated as

MMFMMICV

TGSC

A.1.4 Refere c s doc me ts

– C R Osterwald et al “The res lts of the PEP’9 intercomp rison of ref eren e cel

cal bration an newer tec nolog p rf orman e me s rements: Final Re ort , NREL/TP

-5 0-2 4 7 (19 8) 2 9 p ges

– C R Osterwald et al “The world photovoltaic s ale: an international referen e cel

cal bration program”, P ro res in Ph tovolt aics 7 (19 9) 2 7-2 7

– K Emery “The res lts of the First World Photovoltaic Scale Recal bration”, NREL/TP-5

0-– Winter el al “The res lts of the Secon World Photovoltaic Scale Recal bration”, Proc of

the 31

st

IEEE PVSC 3-7 Jan ary 2 0 , Orlan o, Florida, USA, p 101 -1014

A 2 Global sunl ght method

The esta ls ment of trace bi ty is b sed on the cal bration u in the Contin ou Su -an

-Shade Method as des rib d in ISO 9 4 The referen e solar cel to b cal brated is

comp red u der natural s nl g t with two ref eren e radiometers, namely a pyrhel ometer

me s rin direct solar ir adian e an a pyranometer me s rin dif f use solar ir adian e by

a plcation of a contin ou s ade device u der normal in iden e con ition The total solar

ir adian e is determined by the s m of direct ir adian e an dif f use in-plane ir adian e As a

pyrhel ometer, a secon ary stan ard is u ed in the f orm of an a solute cavity radiometer

comp red at 5-ye r intervals with the World Stan ard Group (WSG) esta l s in the World

Radiometric Referen e (WRR) The cal bration factor for the photovoltaic referen e cel is

determined f rom the me s red s ort circ it c r ent, s aled to 1 0 0 W/m

2

an cor ected for

sp ctral mismatc (IEC 6 9 4-7) b sed on the me s red sp ctral ir adian e of the glo al

s nl g t an the relative sp ctral resp n e of the ref eren e solar cel to b cal brated

Un er certain con ition the simpl f ied glo al s nl g t method is a plca le The s ort-circ it

c r ent of the referen e cel is s aled to 1 0 0 W/m

2

an then ploted vers s pres ure

cor ected ge metric air mas The calbration value is determined fom a l ne r le st s uare

f it at air mas 1,5 A sp ctral mismatc cor ection is not req ired an hen e the

me s rements of the sp ctral ir adian e of the s nl g t an the sp ctral resp n e are not

neces ary In the simpl fied version of the glo al s nl g t method no expl cit sp ctral

mismatc cor ection is p rormed an it is re laced by con ition whic s ould en ure that

the sp ctral ir adian e of the natural s nl g t is s ff i iently close to the defined stan ard

sp ctral ir adian e (IEC 6 9 4-3) that the u certainty comp nent is smal er than q oted in

Ta le A.1 Althou h this s ould b en ured by the con ition l sted in the des ription of the

method b low, it s ould b expl citly verif ied (pref erential y by u in the glo al s nl g t

method) After this val dation the simpl f ied version can b a pl ed as lon as the b u dary

con ition are the same as d rin the val dation

NOT 1 Th v rif i atio a d v ld tio wi pro u e n meric l v lu s for b th meth d If th a re me t b twe n

th s n meric l v lu s is within th u c rtainty b d et of th meth d , th simplfie meth d s al b d eme

v ld te

NOT 2 Th simplfie pro e ure giv s a c rate re ults f or d vic s with a s e tral re p n e o er a bro d ra g

of th s lar s e trum e.g cry tal n si c n d vic s Sig if i a t er ors ma b intro u e f or n row s e tral

re p n e d vic s

A.2.1 Equipme t

a) A mou tin platform, whic can b oriented normal to the s n within an ac urac of ± ,5°

throu hout the cal bration ru

b) A cavity radiometer, trace ble to WRR

c) A pyranometer, trace ble to WRR

d) A s adin device to provide s ade to item c) The f ield an le, viewin an le an a erture

an le provided by the s ade s al comp n ate the resp ctive des riptive an les of the

cavity radiometer of item b)

e) A temp rature control ed mou tin bloc f or the ref eren e device u der test ca a le of

maintainin the cel temp rature at (2 ± 2)°C throu hout al cal bration ru s

f) Trace ble me n to me s re the s ort circ it c r ent of the solar cel to an ac urac of

± ,1 % or b t er

g) Trace ble me n to me s re the sig al of the pyranometer to an ac urac of ± ,5 % or

b t er

h) A sp ctroradiometer ca a le of me s rin the sp ctral ir adian e of the total in-plane

natural s nl g t in the wavelen th ran e of 3 0 – 2 5 0 nm (or larger)