Photovoltaic effect produced in silicon solar cells by x-rays and gamma rays

T he ope n-circuit voltage a nd photoc ur-rcnt produced in a silicon sola r cell by X-a nd gamma rays we re meas ured as a function of expos ure dose ra te, cell temperature, angle of i ncide nce of radi ation, a nd p hoto n e nergy . This photore ponse was s table a nd proportion al t o t he exposure dose rate, which was app li ed up to a maximum of J.8 X lOo roe ntgen per minute for X -rays a nd 4 X 102 roe ntgen per minute for C060 gamm a rays. At a n expos ure dose rate of 1. roentgen per mi n ute t he response was of the orde r of 10-5 vo l t for t he ope n-circuit voltage a nd 10-8 a mpere for the photocurrent. At high exposure dose rates of Cooo gam ma rays, rad iation damage became appare nt. The temperatu re dependence of the photorespo nse was controll ed by the te mpera ture de pendence of t he cell res istance. The directional depe ndence of t he photo res ponse va ri ed wit h t he quality of radiation a nd for Cooo gamma r ays was ver y s mall for a ngles from 0 to 70 . The photoresponse d ecreased with incr easin g p hoton energy but cha nged o nl y litt le between 200 a nd 1,250 kilo electr on vo lts. The ratio of the re ponse t o X-rays of 38 k ilo elect ron volts effe ctive e nergy a nd t ha t to CoGO ga mma rays was approx im a tel." 6:1. An app roxi mate value of t he t hi ckn ess of t he effec tive p-n jUllction layer is deduced from the en ergy depend ence.