High power conversion efficiency of intermediate band photovoltaic solar cell based on Cr-doped ZnTe

- Cr-doped ZnTe thin films were deposited by pulsed laser deposition.
- ZnTe:Cr thin film with 3.5 at% Cr showed an intermediate band structure.
- ZnTe:Cr based intermediate band solar cell exhibited highest PCE of 5.9%.

We report on a high-performance intermediate band solar cell (IBSC) based on Cr-doped ZnTe (ZnTe:Cr) fabricated using a pulsed laser deposition (PLD) method. Chromium (Cr) was uniformly distributed in the ZnTe:Cr thin film with an atomic concentration of about 3.5%, and the ZnTe:Cr thin film showed p-type electrical conductivity. The ZnTe:Cr thin film had higher absorption coefficients than those of undoped ZnTe films in the photon energy range below band gap of ZnTe (2.2 eV). The enhanced absorption coefficients of the ZnTe:Cr thin film were attributed to the photoionization energy between Cr2+ and Cr+ (Cr2+⇌ Cr+), which acted as the IB to absorb photons below the bandgap of ZnTe (2.2 eV). Illumination with an AM 1.5G solar spectrum on the ZnTe:Cr IBSC generated a large short circuit current of 21.18 mA/cm2, an open circuit voltage of 0.48 V, and a fill factor of 0.58, yielding a power conversion efficiency (PCE) of 5.9%, the highest reported PCE in an IBSC based on impurity-doped ZnTe.

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