Conclusions
The IHfO:H films (Hf/In ratio=4 % in target, ~3.87±0.04 % in the films) with various H2 concentrations (0-1.5 %) were prepared at room temperature by a low-damage RPD method, followed by post annealing in air atmosphere at different temperatures (100~250 °C). Under an annealing temperature of 200 °C, the hydrogen concentration hardly changes the crystallinity and the optical properties of the annealed IHfO:H films. The Hall mobility increases from 58.44 cm2V-1s-1 to 102.92 cm2V-1s-1 as the H2 concentration increases from 0 % to 0.8 % mainly due to the hydrogen doping and the related reduction of the oxygen vacancy concentration. However, higher H2 concentration of above 0.8% makes the Hall mobility decrease and the carrier concentration increase, which is probably due to the increasing of the interstitial and substitutional hydrogen in the IHfO:H films. Post annealing increases the crystallinity of the IHfO:H films and reduces their oxygen vacancy, causing Hall mobility to rise from 41.8 cm2V-1s-1 to 102.92 cm2V-1s-1and carrier concentration to decrease from 6.11×1020cm-3 to 1.75×1020cm-3 after 200 °C annealing for the IHfO:H films prepared with optimized 0.8% H2 concentration. At meanwhile, the average TTe of the IHfO:H films increases from 88.54 % to 91.16 % in the visible region and from 77.14 % to 95.61 % in the NIR region. The significant reduced FCA of the IHfO:H films leads to the long wavelength response improvement in the EQE and 0.84 mA/cm2 increase in Jsc for the SHJ solar cell. An efficiency of over 25% was achieved on the SHJ solar cells using IHfO:H films as the front-side TCO layer.