Development of Thin Film Amorphous Silicon Tandem Junction Based Photocathodes Providing High Open-Circuit Voltages for Hydrogen Production

Abstract

Hydrogenated amorphous silicon thin film tandem solar cells (a-Si:H/a-Si:H) have been developed with focus on high open-circuit voltages for the direct application as photocathodes in photoelectrochemical water splitting devices. By temperature variation during deposition of the intrinsic a-Si:H absorber layers the band gap energy of a-Si:H absorber layers, correlating with the hydrogen content of the material, can be adjusted and combined in a way that a-Si:H/a-Si:H tandem solar cells provide open-circuit voltages up to 1.87 V. The applicability of the tandem solar cells as photocathodes was investigated in a photoelectrochemical cell (PEC) measurement set-up. With platinum as a catalyst, the a-Si:H/a-Si:H based photocathodes exhibit a high photocurrent onset potential of 1.76 V versus the reversible hydrogen electrode (RHE) and a photocurrent of 5.3 mA/cm2at 0 V versus RHE (under halogen lamp illumination). Our results provide evidence that a direct application of thin film silicon based photocathodes fulfills the main thermodynamic requirements to generate hydrogen. Furthermore, the presented approach may provide an efficient and low-cost route to solar hydrogen production.

Versatility of doped nanocrystalline silicon oxide for applications in silicon thin-film and heterojunction solar cells

“…2 offered a high contrast in n with respect to the n-type a-Si:H layer above it, thereby effectively increasing the reflection of light towards the sub-cells above the IR. Accordingly, a high combined current of 15.1 mA cm -2 was achieved for the first and the second a-Si:H sub-cell, which is comparable to a-Si/a-Si tandem solar cells with silver back reflectors [40]. Furthermore, an FF of 74 % was achieved in the triple junction solar cell.…”

a-Si:H/µc-Si:H tandem junction based photocathodes with high open-circuit voltage for efficient hydrogen production

“…4,5 Although the a-Si:H/a-Si:H photocathode, shown in Fig. 9, exhibits a high E onset over 1.56 V versus RHE, and is therefore suitable for self-contained water splitting (including overpotentials), 8,20 the photocurrent density is low compared to the a-Si:H/lc-Si:H photocathodes, which limits the overall water splitting efficiency. The a-Si:H/lc-Si:H based photocathodes provide significantly higher photocurrents (Table II and indicated in Fig.…”

“…The substrate temperature for the lc-Si:H and a-Si:H absorber layers was 180 and 130°C, respectively. 20 Amorphous intrinsic buffer layers were deposited with a SC of 10% and a T S of 180°C. Single and tandem junction solar cells were deposited on 100 cm 2 textured aluminum-doped ZnO coated glass substrates.…”

“…The development and application of a-Si:H/a-Si:H photocathodes with platinum catalyst are discussed in detail in Ref. 20.…”

Photoelectrochemical and Photovoltaic Characteristics of Amorphous‐Silicon‐Based Tandem Cells as Photocathodes for Water Splitting

“…Detailed information about the deposition process can be found elsewhere. [13] The solar cells consist of a stack of two amorphous silicon p-i-n cells, which are deposited in a superstrate geometry. The top n-silicon layer is covered with an approximately 700 nm thick silver layer which acts at the same time as the back contact and as a passivation layer of the cell.…”