Investigation into the current loss in InAs/GaAs quantum dot solar cells with Si-doped quantum dots

Shun Chan,Dongyoung Kim,Xiao Li,Huiyun Liu,Mingchu Tang

doi:10.1088/1361-6463/ab4147

Abstract

Our previous studies have shown that introducing Si doping in quantum dots (QDs) can help QD solar cells achieve higher voltage. However, this improvement came at the cost of current loss. In this work, we continue to investigate the cause of the current loss and propose a method to recover it without compromising the voltage. Photoluminescence measurements have confirmed that optimizing the thickness of the GaAs layers in the i-region can lead to strong current gain (~14%) with minimal voltage loss (<3%) and alteration of the QD quality. The capacitance–voltage measurement results support that the current gain mainly originates from the increased depletion width.

Highlights

There is no doubt that recent discoveries with CdSe quantum dot (QD) solar cells (SCs), polymer SCs, and in particular, perovskite SCs have made a huge impact on the photovoltaic research field, merited by their cost-effectiveness and environ mental-friendliness
Much attention has been drawn towards the novel SCs in recent years, QD solar cells (QDSC) have made solid progress towards their theoretical maximum efficiency [4,5,6,7,8]
We continue to investigate the current loss caused by QD Si doping in InAs/GaAs QDSCs, and propose a solution to maintain a high level of Si doping without reducing the width of the depletion region

Summary

Introduction

There is no doubt that recent discoveries with CdSe quantum dot (QD) solar cells (SCs), polymer SCs, and in particular, perovskite SCs have made a huge impact on the photovoltaic research field, merited by their cost-effectiveness and environ mental-friendliness. The cell performance was very promising as the InAs QDs promoted sub-bandgap absorption and a large enhancement in current density [11, 12] Such an improvement was undermined by the voltage loss; the formation of wetting layers below the QDs can increase the dimensionality of the QDs to quantum wells (QWs) leaving the device susceptible to thermal carrier escape [13, 14]. As the effective area of absorption of SCs are proportional to W, this in turn decreases the current output of the SCs. In this work, we continue to investigate the current loss caused by QD Si doping in InAs/GaAs QDSCs, and propose a solution to maintain a high level of Si doping without reducing the width of the depletion region. Capacitance– voltage (C–V) measurements have provided solid evidence for the shrinkage of the depletion width after Si doping (500 nm to 176 nm) and the lengthening of the depletion width with additional intrinsic layers (176 nm to 260 nm)

Experimental work

Results and discussion

Conclusion