# Optimizing carrier collection in solar cells through nanoscale junction design

## TL;DR

This paper shows how adjusting the junction geometry in solar cells can improve their voltage and efficiency by reducing recombination losses.

## Contribution

The study introduces a theoretical approach to optimize solar cell performance by reducing junction contact area.

## Key findings

- Reducing junction contact area lowers reverse saturation current and increases open-circuit voltage by up to 100 mV.
- Using non-absorbing transport layers like TiO2 can boost power conversion efficiency by up to 1.45%.
- Smaller contact areas increase series resistance, which limits overall efficiency gains.

## Abstract

A key challenge in thin-film photovoltaics is achieving selective carrier collection that minimizes recombination losses while maintaining efficient charge extraction. This study presents a theoretical analysis of how reducing junction contact area can enhance the open-circuit voltage (VOC) and the power conversion efficiency (PCE) in thin-film solar cells. Using a zinc-phosphide (Zn3P2) -based heterojunction as a model, we simulate the effect of geometrically minimizing contact via silicon-dioxide (SiO2) layers with patterned holes. The smaller the contact area, the lower the reverse saturation current, which results in a significant increase in the VOC up to 100 mV. However, the reduced contact area also increases the series resistance, thereby limiting the gain in PCE. This approach is especially effective with non-absorbing highly-doped transport layers, such as titanium-dioxide (TiO2) (PCE gain up to 1.45%). This work underscores the importance of balancing reduced recombination with parasitic resistance and current crowding for optimal performance.

This work shows how purely the junction geometry can improve the open circuit voltage in thin film solar cell devices.