Transition metal nitride contacts for CdTe photovoltaics

Abstract

CdS/CdTe thin film photovoltaics were produced with transition metal nitrides (TMNs) as back contacts. The devices show photovoltaic activity but a significant Schottky barrier was found at the back contact. Solar cells perform better as the ZrN films are thicker due to improved microstructure. The good reflectance of ZrN makes it acts as a reflective layer to reduce optical losses and lower the thickness of CdTe. Pure N2 plasma treatment of the back surface of the CdTe and annealing did not improve the performance. A thin layer of Cu was introduced to dope the CdTe and completed with a ZrN film but more amount of Cu deteriorates the performance. Although the nitrides are highly stable and have good electrical properties, wehave not been able to obtain devices to date that are not limited by the back contacts.

Passivating Contacts for Crystalline Silicon Solar Cells: An Overview of the Current Advances and Future Perspectives

“…In addition to TMOs, the exploration of transition metal nitrides has intensified, driven by their advantageous electrical conductivity and thermal stability. [ 222 ] Initially, tantalum nitride (TaN x ) films, introduced through ALD, have proven to be effective ESCs for c‐Si solar cells, offering moderate surface passivation and substantially reducing ρ c . A hybrid solar cell incorporating a single‐layer TaN x rear contact has even achieved an efficiency of over 20%.…”

CdTe Photovoltaics in Superstrate Geometry–Back-Contact Materials: A Review

“…Utilizing metal nitride-based back contacts is still in the infant stage, and an advantage over well-established back contacts is yet to be achieved. The ZrN-based back contact achieved a PCE of 1.68% with a fill factor of 27.83% 103 and an efficiency of 11.9% with a 120-nm-thick layer of MoN x with a fill factor of 68.6%. 105 Etching of the CdTe absorber layer is essential to forming a proper back contact with the CdTe absorber layer.…”

“…Compared to the metal oxides, the work on pnictides as back contacts in CdTe solar cells is less. The possibility of ZrN and MoN x − as a substitute for conventional Cu back contact for CdTe also indicated that Cu in the back-contact layer is needed to improve the efficiency of the cell. Utilizing metal nitride-based back contacts is still in the infant stage, and an advantage over well-established back contacts is yet to be achieved.…”

Novel Contact Materials for Improved Performance CdTe Solar Cells Final Report

“…Final Status Summary: TiN and ZrN transition metal nitrides were tested and found to produce Schottky contacts regardless of heat treatment. [9] CIS:N was tested and found to produce unsatisfactory contacts. Amorphous Si:H was tested and found to degrade the performance of the CdTe devices over time.…”