# US 12,191,415 B2 · Multi-junction photovoltaic cell having wide bandgap oxide conductor between subcells and method of making same

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- Number: US 12,191,415 B2
- Document ID: US12191415B2
- Status: Granted
- Kind: B2
- Application number: 16/396,495
- Filed: 2019-04-26
- Published: 2019-10-31
- Granted: 2025-01-07
- Earliest claimed: 2018-04-26
- Assignees: California Institute of Technology
- Applicants: California Institute of Technology
- Inventors: Stefan Omelchenko; Sisir Yalamanchili; Nathan S Lewis
- Web page: https://patentgrep.com/patent/US12191415B2

## CPC

- H10K 30/87: Light-trapping means
- H10F 10/161: comprising multiple PN heterojunctions, e.g. tandem cells
- H10F 71/128: {Annealing}
- H10F 77/1223: characterised by the dopants
- H10F 77/315: {the coatings being antireflective or having enhancing optical properties}
- H10K 30/40: comprising a p-i-n structure, e.g. having a perovskite absorber between p-type and n-type charge transport layers
- H10K 85/50: Organic perovskites; Hybrid organic-inorganic perovskites [HOIP], e.g. CH3NH3PbI3
- H10K 30/50: Photovoltaic [PV] devices
- Y02E 10/549: Organic PV cells
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

Increasing the power conversion efficiency of silicon (Si) photovoltaics is a key enabler for continued reductions in the cost of solar electricity. Disclosed herein is a multi-junction photovoltaic cell that does not utilize a conventional interconnection layer and instead places a wide bandgap oxide conductor, for example, a metal oxide such as TiO2, between a top light absorption layer having a relatively large bandgap and a bottom light absorption layer having a relatively small bandgap. The advantageous omission of a conventional interconnection layer between the two subcells is enabled by low contact resistivity between the top and bottom light absorbing layers provided by the wide bandgap oxide conductor. The absence of the conventional interconnect between the subcells significantly reduces both optical losses and processing steps. The disclosed photovoltaic cell may thus enable low-cost, high-efficiency multi-junction devices through less complex manufacturing processes and lower material costs.

## Claims

### Claim 1

A multi-junction photovoltaic cell, comprising:
a first light absorption layer comprising perovskite;
a second light absorption layer; and
a wide bandgap oxide conductor comprising
a compact titanium dioxide layer (cp-TiO2);
a mesoporous titanium dioxide layer contacting the compact titanium dioxide layer;
wherein the first light absorption layer contacts the mesoporous titanium dioxide layer;
wherein the second light absorption layer contacts the cp-TiO2 layer; and
wherein a band alignment between the cp-TiO2 and the second light absorber comprises an ohmic contact with a resistivity less than 30 mΩcm2; and
wherein the cp-TiO2 layer is formed by atomic layer deposition (ALD) with tetrakisdimethylamidotitanium (TDMAT) and annealed at about 400° C.

### Claim 2 (depends on 1)

The multi-junction photovoltaic cell of claim 1, wherein the second light absorption layer includes a silicon substrate that includes a p-type doped emitter region.

### Claim 3 (depends on 1)

The multi-junction photovoltaic cell of claim 1, wherein the second light absorption layer includes n-type silicon.

### Claim 4 (depends on 1)

The multi-junction photovoltaic cell of claim 1, wherein a second light absorption layer is a homojunction cell.

### Claim 5 (depends on 1)

The multi-junction photovoltaic cell of claim 1, wherein:
a Spiro-OMeTAD layer contacting the first light absorption layer;
an MoOx layer contacting the Spiro-OMeTAD layer;
a transparent conductor layer contacting the MoOx layer; and
a conductor layer contacting the transparent conductor layer.

### Claim 6 (depends on 5)

The multi-junction photovoltaic cell of claim 5, wherein the conductor layer includes a metal grid.

### Claim 7

A two-terminal tandem photovoltaic cell, comprising:
a first subcell including a first light absorption layer of perovskite material;
a second subcell including a second light absorption layer of a semiconductor; and
a large bandgap oxide conductor layer contacting the perovskite material and the semiconductor, wherein the large bandgap oxide conductor layer provides an ohmic contact with a resistivity less than 30 mΩcm2; and
wherein the large bandgap oxide conductor layer is formed by atomic layer deposition (ALD) with tetrakisdimethylamidotitanium (TDMAT) and annealed at about 400° C.

### Claim 8 (depends on 7)

The two-terminal tandem photovoltaic cell of claim 7, wherein the second subcell is a crystalline silicon homojunction subcell.

### Claim 9 (depends on 7)

The two-terminal tandem photovoltaic cell of claim 7, wherein the oxide conductor layer includes:
a compact titanium dioxide layer contacting a crystalline p-type emitter; and
a mesoporous titanium dioxide layer contacting the compact titanium dioxide layer; and wherein
the first subcell includes:
a perovskite layer contacting the mesoporous titanium dioxide layer;
a Spiro-OMeTAD layer contacting the perovskite layer;
an MoOx layer contacting the Spiro-OMeTAD layer;
an IZO layer contacting the MoOx layer; and
a conductor layer contacting the IZO layer.

### Claim 10 (depends on 9)

The two-terminal tandem photovoltaic cell of claim 9, further comprising an anti-reflective layer formed over the IZO layer and conductor layer.