Light-emitting diodes (LEDs), LED arrays, and related devices are disclosed. An LED device includes a first LED chip and a second LED chip mounted on a submount with a light-altering material in between. The light-altering material may include at least one of a light-reflective material and/or a light-absorbing material. Individual wavelength conversion elements may be arranged on each of the first and second LED chips. The light-altering material may improve the contrast between the first and second LED chips as well as between the individual wavelength conversion elements. LED devices may include submounts in modular configurations where LED chips may be mounted on adjacent submounts to form an LED array. Each LED chip of the LED array may be laterally separated from at least one other LED chip by a same distance and a light-altering material may be arranged around the LED array.