Enhancement of interface transportation for quantum dot solar cells using ultrathin InN by atomic layer deposition

Abstract

Quantum dot-sensitized solar cells have gained rapid development which could produce potential applications. Although they have a theoretical photoelectric conversion efficiency of 44%, there is still a considerable gap in comparison with corresponding practical solar cells, which is mainly due to the fact that the interface transfer, stability and efficiency improvement are still facing some problems. In particular, the carrier recombination loss at the cell interface seriously hinders the quantum dot-sensitized solar cells from developing. In this work, an ultra-thin layer of InN prepared by plasma-enhanced atomic layer deposition is inserted into the FTO/TiO₂ interface of the photoanode of CdSeTe based quantum dot-sensitized solar cells to improve the performance of the photoanode structure, and physical mechanism behind the device is discussed. We first investigate the effects of different deposition temperatures (170, 200 and 230 ℃) on the cell performance of InN films. While the InN ultra-thin layer is deposited at 200 ℃, an enhancement of 16.9% in conversion efficiency is achieved as compared with the reference group. Then, the effects of different thickness (5, 10, and 15 cycles) on the cell are investigated at a fixed deposition temperature of 200 ℃. Additionally, an improvement of fill factor for the device after an introduction of InN layer is observed. This enhancement is further convinced by an apparent reduction of series resistance extracted by the Nyquist curve. The significant increase in fill factor indicates that the introduction of InN accelerates the extraction, transfer and separation of electrons, and reduces the possibility of photon-generated carriers recombination. However, the insertion of InN deposition temperature and thickness have a certain range of enhancement in the cell performance, and further investigation of the mechanism will be carried out.