Stable Molybdenum Nitride Contact for Efficient Silicon Solar Cells

Abstract

Carrier‐selective passivating contacts play a crucial role in highly efficient silicon solar cells targeting the cost‐effective photovoltaic industry. Widely developed hole‐selective passivating‐contact molybdenum oxide (MoOx) exhibits inferior long‐term stability induced by chemical reactions between the MoOx and the adjacent metals. Herein, low‐temperature magnetron‐sputtering‐deposited molybdenum nitride (MoNx) films are developed as stable hole‐selective passivating contacts for crystal silicon solar cells. The work function of the MoNx films can be as deep as 5.62 eV featuring a low resistivity of 5.0 × 10−4 Ω cm by optimizing the deposition process. Quasi‐metallic MoNx integrated with a MoOx passivating layer is verified to act as effective hole‐selective passivating contacts for crystal silicon solar cells, yielding a power convertion efficiency (PCE) above 17%. Although the hole‐selective passivation of MoNx films is inferior to fresh MoOx ones, the device performance with MoNx film is kept stable with time in air exposure and surpasses MoOx films after 6 months. The stable performance is ascribed to the metal electrodes diffusion barrier and insusceptible work function of MoNx films compared to MoOx films. This work makes a preliminary exploration to develop efficient crystal silicon solar cells with stable and cost‐effective metal nitrides as hole‐selective passivating contacts.

Dopant‐free passivating contacts for crystalline silicon solar cells: Progress and prospects

“…The employment of TaN x between c ‐Si and Al restrains the carrier recombination and reduces ρ c at the rear surface, thus significantly improving the efficiency of c‐ Si solar cells from 16.1% to 20.1%. In comparison, a much smaller fraction of materials have been suggested with potentials as HTL, including CuI, 116 Cu 2 S, 113 and MoN x 58 – this topic remains to be further exploited.…”

“…In order to reduce the parasitic absorption loss induced by the doped Si film in SHJ or TOPCon solar cells, wide band gap materials have been proposed to replace doped Si. Moreover, they can be prepared by simple deposition techniques, such as thermal/e-beam evaporation, 54,55 atomic layer deposition (ALD), 56,57 sputtering, 58,59 and solution-based processing. 60,61 These materials mainly facilitate the transport of carriers with desired polarity to the relevant contact, for which they are termed as carrier transport layer (CTL) throughout the discussion.…”

“…[48][49][50]52,[54][55][56]59,62,63,80,93,96,97,99,100,111,114,116,121,132,169,172,200,201,215,217,220,[239][240][241][242][243][244][245][246][247][248][249][250][251] c-Si solar cells from 16.1% to 20.1%. In comparison, a much smaller fraction of materials have been suggested with potentials as HTL, including CuI, 116 Cu 2 S, 113 and MoN x 58 this topic remains to be further exploited.…”

Magnetron Sputtered Thin Films Based on Transition Metal Nitride: Structure and Properties

“…Because of its outstanding features, MoN films find their applications in the fields such as hard coating in cutting tools, [233] microelectronics, [234] solar cells, [235] MEMS devices, [224] fuel cells, [236][237][238] super conductors, [239][240][241][242][243] diffusion barriers, [230,244] Li-ion batteries, [245] etc.…”

High-performance perovskite/silicon heterojunction solar cells enabled by industrially compatible post annealing

“…12,13 Dopant-free contacts are expected to reduce the parasitic optical absorption and Auger recombination as well as simplifying the fabrication process. Up till now, various metal oxides, [14][15][16][17][18] fluorides, [19][20][21] nitrides, [22][23][24] oxynitride, 25,26 oxyfluoride and organic polymers, [27][28][29] have been demonstrated as hole-or electron-transport layers for c-Si solar cells. Due to considerable efforts devoted to this topic, the PCE of c-Si solar cells with dopant-free carrier-selective contacts has increased rapidly in these years.…”