22.6% Efficient Solar Cells with Polysilicon Passivating Contacts on n‐type Solar‐Grade Wafers

Abstract

Czochralski (Cz)‐grown upgraded metallurgical‐grade (UMG) silicon wafers degrade significantly during high‐temperature processes, eroding their appeal as a low‐cost alternative to conventional electronic‐grade silicon wafers. However, the thermal degradation in UMG wafers can be delayed by utilizing a prefabrication annealing step. Based on this, a high‐efficiency solar‐cell process is modified by selecting a single‐boron diffusion step and applying phosphorus‐doped polycrystalline films as electron‐selective contacts with excellent impurity‐gettering properties to minimize the thermal budget. The application of this modified high‐efficiency solar‐cell process to n‐type UMG‐Cz wafers results in a solar cell with a conversion efficiency of 22.6% on a cell area of 2 × 2 cm2.

Polysilicon passivated junctions: The next technology for silicon solar cells?

“…The data were obtained from references. 7,11,27,54,56,59,[63][64][65][66][67][68][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][88][89][90][91][92][93][94][95][96][97][98]110 ll free charge carriers present in the poly-Si layer absorb infrared photons, much in the same way as they do in c-Si. 110 This loss also occurs when the poly-Si layer is placed at the back of a solar cell, amounting to 0.3-0.5mA/cm 2 (depending on doping) for a 140-nm-thick poly-Si layer.…”

“…Non-textured = J 0 measured on planarized surfaces,Textured = J 0 measured on textured surfaces. The data were obtained from references 7,11,27,54,56,59,[63][64][65][66][67][68][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][88][89][90][91][92][93][94][95][96][97][98]110.…”

Effect of Al Electrodes on Surface Passivation of TiOx Selective Heterocontacts for Si Solar Cells

“…This step is critical to the implementation of heterocontacts in solar cell fabrication, which requires thermal annealing at 250–300 °C for improving surface passivation and lowering contact resistance. [ 21,29 ]…”

Ultra‐Thin Poly‐Si Layers: Passivation Quality, Utilization of Charge Carriers Generated in the Poly‐Si and Application on Screen‐Printed Double‐Side Contacted Polycrystalline Si on Oxide Cells

“…Passivating contacts facilitate the realization of highly efficient silicon solar cells. [ 1–5 ] Currently many research groups work on passivated contacts based on polycrystalline Si on oxide (POLO) or related junction schemes, applying different approaches for their implementation into industrial solar cells. [ 6–9 ] One approach is to apply nonpatterned POLO contacts for both polarities on the cell front‐ and rear side.…”