Analysis of GaAs solar cells at High MOCVD growth rates

Abstract

Single junction GaAs solar cells grown by MOCVD are fabricated over a range of growth rates targeting up to 56 µm/hr in order to evaluate the effect on photovoltaic device performance. MOCVD recipe conditions are provided. Dopant incorporation efficiency is found to increase at high growth rates, potentially due to reduced Zn desorption as the time required to deposit a monolayer of GaAs is reduced. Device results are characterized by light and dark-IV as well as external quantum efficiency and verified against bulk minority carrier lifetime data from time-resolved photoluminescence. High growth rate solar cells degrade less than 4% relative to baseline devices with Voc and Jsc losses of 1% and 3%, respectively. The comparison suggests that both bulk Shockley Read Hall (SRH) lifetime and surface recombination velocity (SRV) are affected by growth rate and contribute to a reduction in performance.

24.5% efficient GaAs p-on-n solar cells with 120 µm h−1 MOVPE growth

“…Much effort has been devoted recently to reduce the cost of GaAs based solar cells including the epitaxy cost, generally by metalorganic vapor phase epitaxy (MOVPE). This can be achieved by either increasing the GR (decrease machine overhead time) or improving material (source) utilization [6][7][8]. From price per watt analysis, the reduction in the overhead time of MOVPE reactors, together with the improvement in material utilization efficiency, can reduce the cost of GaAs single junction solar cells by 74%, when the GR of GaAs is boosted from 14 to 56 µm h −1 with performance loss less than 1% [7,8].…”

“…This can be achieved by either increasing the GR (decrease machine overhead time) or improving material (source) utilization [6][7][8]. From price per watt analysis, the reduction in the overhead time of MOVPE reactors, together with the improvement in material utilization efficiency, can reduce the cost of GaAs single junction solar cells by 74%, when the GR of GaAs is boosted from 14 to 56 µm h −1 with performance loss less than 1% [7,8]. Recently, GaAs n-on-p solar cells grown at a speed of 100 µm h −1 have been recently reported with a high conversion efficiency of 23.6% under AM1.5G condition [9].…”

Status and challenges of multi-junction solar cell technology

“…Reduction processes in dopant precursor flows at higher growth rates of 56 μm/h causes an electronic degradation of the solar cell by approximately 4%. The increase in growth rate, however, can reduce production costs by 74% and cycle time from 42 to 15 min (Schmieder et al, 2014). After the MOVPE stack is complete, chemical etching and photolithography is used to pattern the GaAs top layer, followed by electroplating of the front metal grid and deposition of the ARC layer by plasma enhanced chemical vapor deposition (PECVD).…”

Impact of the III-V/Ge nucleation routine on the performance of high efficiency multijunction solar cells

“…In this way, the sole impact of these designs in initial single junctions and subsequently in complete 3JSCs can be decoupled. This work might also help to understand the potential gains in V OC of MOVPE processes using high growth rates and therefore minimizing the thermal load [23,24], as well as the possibility of using lower growth temperature ranges preserving the good quality of the epilayers.…”