An imaging device may include an image sensor having an array of image pixels. The array of image pixels may include one or more infrared pixels that are configured to detect infrared light. The infrared pixels may include reflective structures for increasing quantum efficiency in the infrared spectral range. The reflective structures may include first and second parallel structures formed on opposing sides of a photodiode in an infrared pixel. The reflective structures may be partially transparent to infrared light and non-transparent to visible light. The reflective structures may form an optical cavity so that infrared light that enters an infrared pixel is reflected back and forth between the reflective structures until it is absorbed by the photodiode in the infrared pixel. Reflective structures may also be formed between infrared filters and color filters to suppress optical crosstalk between infrared pixels and color pixels.