Rectification and tunneling effects enabled by Al2O3 atomic layer deposited on back contact of CdTe solar cells

Abstract

Atomic layer deposition (ALD) of Aluminum oxide (Al2O3) is employed to optimize the back contact of thin film CdTe solar cells. Al2O3 layers with a thickness of 0.5 nm to 5 nm are tested, and an improved efficiency, up to 12.1%, is found with the 1 nm Al2O3 deposition, compared with the efficiency of 10.7% without Al2O3 modification. The performance improvement stems from the surface modification that optimizes the rectification and tunneling of back contact. The current-voltage analysis indicates that the back contact with 1 nm Al2O3 maintains large tunneling leakage current and improves the filled factor of CdTe cells through the rectification effect. XPS and capacitance-voltage electrical measurement analysis show that the ALD-Al2O3 modification layer features a desired low-density of interface state of 8 × 1010 cm−2 by estimation.

Back contacts materials used in thin film CdTe solar cells—A review

“…Atomic layer deposited (ALD) Al 2 O 3 on TEC™ 10 substrates has also been used to overcome shorts due to pinholes in CdTe solar cells (TEC™ 10/Al 2 O 3 /CdS/CdTe/ZnTe:Cu/Ni). 176 Liang et al (2015) 177 obtained PCE 12.1% using 1 nm thick ALD Al 2 O 3 . Lin et al (2016) 178 achieved PCE of 13.0% (V oc 782 mV, J sc 24.2 mA cm −2 , and FF 68%) with a 9 nm Cu back contact layer followed by a 2 nm ALD-Al 2 O 3 layer.…”

High‐Performance and Industrially Viable Nanostructured SiOx Layers for Interface Passivation in Thin Film Solar Cells

“…Furthermore, SiO x has the potential to be used as a passivation layer in other thin film technologies, such as CdTe, Cu 2 ZnSnS 4 (CZTS), or perovskites, which could allow for an effective defect passivation. [ 36–47 ]…”

Radiative Efficiency and Charge‐Carrier Lifetimes and Diffusion Length in Polycrystalline CdSeTe Heterostructures

“…Alumina passivation reduces interface recombination velocity S int < 100 cm s −1 and correspondingly increases carrier lifetimes to more than 200 ns in polycrystalline double heterostructures (DHs) . The passivation mechanisms are related to interface oxides and charges …”