Erbium doped materials are of great interest in thin film integrated optoelectronic technology, due to their Er3+ intra-4f emission at 1.54 μm, a standard telecommunication wavelength. Er-doped dielectric thin films can be used to fabricate planar optical amplifiers or lasers that can be integrated with other devices on the same chip. Semiconductors, such as silicon, can also be doped with erbium. In this case the Er may be excited through optically or electrically generated charge carriers. Er-doped Si light-emitting diodes may find applications in Si-based optoelectronic circuits. In this article, the synthesis, characterization, and application of several different Er-doped thin film photonic materials is described. It focuses on oxide glasses (pure SiO2, phosphosilicate, borosilicate, and soda-lime glasses), ceramic thin films (Al2O3, Y2O3, LiNbO3), and amorphous and crystalline silicon, all doped with Er by ion implantation. MeV ion implantation is a technique that is ideally suited to dope these materials with Er as the ion range corresponds to the typical micron dimensions of these optical materials. The role of implantation defects, the effect of annealing, concentration dependent effects, and optical activation are discussed and compared for the various materials.

Erbium implanted thin film photonic materials

In the 1980s, advances in the passivation of both cell surfaces led to the first crystalline silicon solar cells with conversion efficiencies above 20%. With today's industry trend towards thinner wafers and higher cell efficiency, the passivation of the front and rear surfaces is now also becoming vitally important for commercial silicon cells. This paper presents a review of the surface passivation methods used since the 1970s, both on laboratory-type as well as industrial cells. Given the trend towards lower-cost (but also lower-quality) Si materials such as block-cast multicrystalline Si, ribbon Si or thin-film polycrystalline Si, the most promising surface passivation methods identified to date are the fabrication of a p–n junction and the subsequent passivation of the resulting silicon surface with plasma silicon nitride as this material, besides reducing surface recombination and reflection losses, additionally provides a very efficient passivation of bulk defects. Copyright © 2000 John Wiley & Sons, Ltd.

Surface passivation of crystalline silicon solar cells: a review

We report the observation of self-doping in perovskite. CH3NH3PbI3 was found to be either n- or p-doped by changing the ratio of methylammonium halide (MAI) and lead iodine (PbI2) which are the two precursors for perovskite formation. MAI-rich and PbI2-rich perovskite films are p and n self-doped, respectively. Thermal annealing can convert the p-type perovskite to n-type by removing MAI. The carrier concentration varied as much as six orders of magnitude. A clear correlation between doping level and device performance was also observed.

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Qualifying composition dependent p and n self-doping in CH3NH3PbI3

The experimentally observed dependence of effective surface recombination velocity Seff at the Si‐SiO2 interface on light‐induced minority carrier excess concentration is compared with theoretical predictions of an ‘‘extended Shockley–Read–Hall (SRH) formalism.’’ The calculations of SRH‐recombination rates at the Si‐SiO2 interface are based on the theory of a surface space charge layer under nonequilibrium conditions and take into account the impact of illumination level, gate metal work function, fixed oxide charge density, and the energy dependence of capture cross sections σn, σp and interface state density Dit. Applying this theory to p‐type silicon surfaces covered by high quality thermal oxides, the experimentally observed strong increase of Seff with decreasing minority carrier excess concentration could quantitatively be attributed to the combined effect of the σn/σp ratio of about 1000 at midgap and the presence of a positive fixed oxide charge density Qf of about 1×1011 charges/cm2. Due to the f...

Impact of illumination level and oxide parameters on Shockley–Read–Hall recombination at the Si‐SiO2 interface

Our unique, high-efficiency c-Si solar cell, named the HIT cell, has shown considerable potential to improve junction properties and surface passivation since it was first developed. The improved properties in efficiency and temperature dependence compared to conventional p – n diffused c-Si solar cells are featured in HIT power 21TM solar cell modules and other applications which are now on the market. In the area of research, further improvement in the junction properties of the a-Si/c-Si heterojunction has been examined, and the highest efficiency to date of 20.1% has recently been achieved for a cell size of 101 cm2. The high open circuit voltage exceeding 700 mV, due to the excellent surface passivation of the HIT structure, is responsible for this efficiency. In this paper, recent progress in HIT cells by Sanyo will be introduced. Copyright © 2000 John Wiley & Sons, Ltd.

HITTM cells—high-efficiency crystalline Si cells with novel structure

Significant improvements in silicon solar cell performance are reported using an improved high‐efficiency silicon solar cell structure. This structure overcomes deficiencies in an earlier structure by locally diffusing boron into contact areas at the rear of the cells. Terrestrial energy conversion efficiencies up to 24% are reported for silicon cells for the first time. Air Mass 0 efficiencies lie in the 20–21% range, the first silicon cells to exceed 20% efficiency under space illumination.

A. Wang

Papers

24% efficient silicon solar cells